questions about autotune

MADMAX · Post by **MADMAX** » Thu May 15, 2008 1:10 am

TopMountGSR wrote:I'm curious when you run such a smooth graph dont your AFRs vary alot and bob up and down [but still in a safe range] as opposed to a notchy non smooth graph that has every cell tuned dead on? I'm just trying to learn here. My graphs are real notchy because I try to tune each cell so precisely to the target afr. Thanks for your help. dk

Nope, every car I tune is really smooth. Those graphs are just an example of what I start with. I tune them from there. The transition from cell to cell should be smooth.

Post by **Bugermass** » Thu May 15, 2008 1:40 am

Some cars you can get really smooth graphs, other cars will have weird spots where smooth doesn't work, usually do to resonances in exhuast or intake manifolds, of you you have like a tiny little turno thats spools quickly.. It really depends on the car.. Its good to always try to get a good smooth graph but its not always possible to do and have a great tune..

MADMAX · Post by **MADMAX** » Sat May 17, 2008 12:08 pm

Bugermass wrote:Some cars you can get really smooth graphs, other cars will have weird spots where smooth doesn't work, usually do to resonances in exhuast or intake manifolds, of you you have like a tiny little turno thats spools quickly.. It really depends on the car.. Its good to always try to get a good smooth graph but its not always possible to do and have a great tune..

Resonance will not make a fuel graph jagged. Resonance doesn't just appear. A motor will ramp up in torque to the point of resonance which will be over a few fuel cells. It will be a hump, nothing more. The other major reason to start with flat fuel curves it that when tuning turbo cars most people will have the boost fuel curves way off (lean) on the lower rpms because on the dyno they will never see that part of the map. IF the motor every loads up all the way and makes boost just slightly earlier, the motor will run lean in that spot.

greasemonkee · Post by **greasemonkee** » Sat May 17, 2008 2:10 pm

MADMAX wrote: Resonance will not make a fuel graph jagged. Resonance doesn't just appear. A motor will ramp up in torque to the point of resonance which will be over a few fuel cells. It will be a hump, nothing more.

Are you referring to exh scavenging? Hope so. Acoustical influence on cylinder filling can do strange things, if you've never seen the evidence tune a couple NA cars.

Post by **Bugermass** » Sat May 17, 2008 2:34 pm

in boost, yes I agree it SHOULD be as smooth as possible, but its not always the case.. There are just some combinations that won't be smooth no matter what you do.. Even just having a map thats too low a resolution can cause jagged results.. For an example look at my E85 high res map in the tuner posted section.. I created a 24 columb N/A map and because of the resolution i was able to get a super super smooth fuel and timming map, but if that map was only 10X10 it would be less smooth due to the larger differences between colums..

zex_cool · Post by **zex_cool** » Sat May 17, 2008 8:06 pm

Bugermass wrote:...For an example look at my E85 high res map in the tuner posted section..

one of the "bad" things, we cant see how the pros do it.

MADMAX · Post by **MADMAX** » Sun May 18, 2008 3:16 am

greasemonkee wrote:
MADMAX wrote: Resonance will not make a fuel graph jagged. Resonance doesn't just appear. A motor will ramp up in torque to the point of resonance which will be over a few fuel cells. It will be a hump, nothing more.
Are you referring to exh scavenging? Hope so. Acoustical influence on cylinder filling can do strange things, if you've never seen the evidence tune a couple NA cars.

I tune N/A motors more than anything. Smooooth is always the case. Unless the car has one of those crappy pos B&M FPRs, then it's a ramp.

crx303 · Post by **crx303** » Sun May 18, 2008 12:38 pm

MADMAX wrote:
greasemonkee wrote:
MADMAX wrote: Resonance will not make a fuel graph jagged. Resonance doesn't just appear. A motor will ramp up in torque to the point of resonance which will be over a few fuel cells. It will be a hump, nothing more.
Are you referring to exh scavenging? Hope so. Acoustical influence on cylinder filling can do strange things, if you've never seen the evidence tune a couple NA cars.
I tune N/A motors more than anything. Smooooth is always the case. Unless the car has one of those crappy pos B&M FPRs, then it's a ramp.

You don't tune with the vac hose disconnected from the B&M FPR?

TopMountGSR · Post by **TopMountGSR** » Sun May 18, 2008 7:32 pm

I used to rock a b&m, it sucked. We could not keep a good tune on the car what so ever. The fuel pressure would vary constantly. Some days it would run lean, some days so pig rich anything less that 50% throttle it would back fire spit and spudder.

Post by **calvin** » Sun May 18, 2008 7:47 pm

i tune cars with b&m with vacuum hose disconnected

Adam Hopkins · Post by **Adam Hopkins** » Sun May 18, 2008 8:22 pm

calvin wrote:i tune cars with b&m with vacuum hose disconnected

Why is that? Correct me if I am wrong but I was under the impression that the reason for the fuel pressure regulator was to decrease fuel pressure under idle and high vacuum, and increase fuel pressure as more fuel was needed. I also was under the impression that when under boost the vacuum line would put pressure on the fuel pressure regulator and raise the fuel pressure, not as much as a FMU, but something on a much smaller scale. I am assuming that you hook the line back up when the customer leaves, That would change the a/f ratio if you tuned it with it disconnected. Right? I can understand if you are trying to keep the fuel pressure constant by removing the vacuum line while your tuning, but if you do hook up the vacuum line when they leave, then you are changing the tune.

z31 · Post by **z31** » Sun May 18, 2008 10:52 pm

Adam your correct in your thinking. It relieves the higher pressure from an upgraded pump, but still increases pressure on a 1:1 basis just like the stock regulator. I would also like to know how Calvin tunes with it disconnected, maybe I'm just not understanding it correctly.

Post by **Gaskleppie** » Mon May 19, 2008 1:12 am

I can explain.... In the early days of eCtune (about 4 years ago) we had a few cars with variating AF's because of variating fpr's. It was my idea to remove the hose to get a stable AF and it helped perfectly! You can get your AF way more stable with the hose disconnected. You remove 1 variable in the system which can change the AF. After tuning we DO NOT connect this hose and tell the owner that this hose is not necessary any more. The only downside is that if the injectors are a just big enough for the turbo setup, it can give problems getting enough fuel. Setting the base fuel pressure a bit higher will solve this.

MADMAX · Post by **MADMAX** » Mon May 19, 2008 1:25 am

Gaskleppie wrote:I can explain.... In the early days of eCtune (about 4 years ago) we had a few cars with variating AF's because of variating fpr's. It was my idea to remove the hose to get a stable AF and it helped perfectly! You can get your AF way more stable with the hose disconnected. You remove 1 variable in the system which can change the AF. After tuning we DO NOT connect this hose and tell the owner that this hose is not necessary any more. The only downside is that if the injectors are a just big enough for the turbo setup, it can give problems getting enough fuel. Setting the base fuel pressure a bit higher will solve this.

The main problem the B&M is that it make the FPR less than 1:1 and kind of variable hence the increasing fuel curve. They are worthless on a turbo car. It is better to use a completely stock one than one of those POS's or spend the extra $130 and get an AEM one on a turbo car. If it's on a N/A motor, it doesn't really effect it. I always wanted to put an pressure sensor on the rail and let the ecu read the fuel pressure and make compensations to the injector pulse. Just a simple calculation in the code.

JaredKaragen · Post by **JaredKaragen** » Mon May 19, 2008 4:50 am

MADMAX wrote:I always wanted to put an pressure sensor on the rail and let the ecu read the fuel pressure and make compensations to the injector pulse. Just a simple calculation in the code.

Sounds like a a feature request; along with finding a source for a hopefully linear sensor that would need to be on a special banjo bolt or something.... But tis a very solid concept there

A little too close to OBD-II for my tastes though